Issue 05/2023

Fibres / Textiles
Textile yarns from
biopolyesters
KORTEKS (Bursa/Türkiye) is one of the largest suppliers
of polyester yarn. In addition, a new plant for processing
recycled polymer has been commissioned with a daily
capacity of 20 tonnes. Korteks is also active in the development
of yarns from various biopolymers. The experimental design
of all yarn developments is carried out on a pilot scale
melt spinning machine with a 5-zone extruder, spinnerets,
quenching line, drawing godets and winder.
In 2017 and 2020, respectively, Korteks started to develop
filament yarns from PLA, PHA, and PBS. After the first
results and observations, industrial trials were carried out
for the three biopolymers.
PLA
PLA has inherent properties such as flame retardancy,
UV resistance, low density, and low-emperature dyeability.
However, the production of PLA fibre/yarn is challenging due
to its hydrolytic degradation and brittle structure.
In an initial research programme, PLA Pre Oriented
Yarn (POY) was spun and then texturised to give volume,
elasticity, and crimp properties like natural fibres. 100, 150,
300 denier PLA filament yarns have been developed on an
industrial scale. In addition, dope dyed coloured texturised
PLA yarns could be produced. PLA filament yarns have
sufficient strength and elongation properties for weaving
and knitting processes. As PLA is sensitive to alkaline
conditions and high temperatures, PLA yarns and fabrics
require some modifications in dyeing. In addition, finishing
processes of PLA fabrics show close processes with PET
fabrics, but considering the chemical properties of PLA,
some modifications should be made with R&D studies.
PBS
Polybutylene succinate (PBS) is an aliphatic polyester that
can be synthesised from both fossil fuels and monomers
derived from biobased feedstocks. Biodegradability and
excellent melt processability make PBS suitable for
sustainable textiles [1]. The fact that its production costs are
lower than PHAs and that it is more ductile than PLA puts
PBS at the forefront. In addition, PBS has a wide processing
temperature range and good thermal stability compared
to other biopolymers.
Due to the high elongation properties of PBS, the
problem of tight winding is often encountered during the
process. Furthermore, in order to eliminate the melt flow
problems, PBS trials are carried out with different ranges of
melt flow rate polymers.
PHA
The production of biodegradable fibres from P3HB has
been investigated by previous researchers on a laboratory
or pilot scale. The common problem was the formation of
irregular, large crystallites with low density, resulting in
inadequate mechanical properties. Various solutions have
been proposed to improve the structure development.
However, none of these studies were suitable for largescale
production. In studies investigating the thermal
behaviour of PHB, it was found that the molecular weight
starts to decrease just above the melting point around 185°C,
and weight loss and chain breaks occur in the polymer
above 200°C. Initial experiments conducted above 180°C
resulted in degraded, discontinuous melt flow. Extruder
temperatures, residence time, and spinneret exit pressure
Figure 1. Samples of PHA and PBS filament yarns
(from left to right respectively, raw POY, air texturized
PHB, and raw POY and texturized PBS)
Figure 2. Samples of PLA filament yarns (from left to
right respectively, raw white POY, FDY, and dope dyed
green POY and DTY bobbins)
28 bioplastics MAGAZINE | Renewable Carbon Plastics [05/23] Vol. 18